Recent years have witnessed practical use of a flat-panel display in various products and fields. This has led to a demand for a flat-panel display that is larger in size, achieves higher image quality, and consumes less power.
Under such circumstances, great attention has been drawn to an organic EL display device that (i) includes an organic electroluminescence (hereinafter abbreviated to “EL”) element which uses EL of an organic material and that (ii) is an all-solid-state flat-panel display which is excellent in, for example, low-voltage driving, high-speed response, self-emitting, and wide viewing angle characteristics.
An organic EL display device includes, for example, (i) a substrate made up of members such as a glass substrate and TFTs (thin film transistors) provided to the glass substrate and (ii) organic EL elements provided on the substrate and connected to the TFTs.
An organic EL element is a light-emitting element capable of emitting high-luminance light by low-voltage direct-current drive. The organic EL element has a structure in which a first electrode, an organic EL layer, and a second electrode are stacked in this order, and the first electrode is electrically connected to the TFT.
As the organic EL layer, an organic layer having a structure in which a hole injection layer, a hole transfer layer, an electron blocking layer, a luminescent layer, a hole blocking layer, an electron transfer layer, an electron injection layer, and the like are stacked together is provided between the first electrode and the second electrode.
For example, a full-color organic EL display device typically includes, as sub-pixels aligned on a substrate, organic EL elements of red (R), green (G), and blue (B). The full-color organic EL display device carries out an image display by, with use of TFTs, selectively causing the organic EL elements to each emit light with a desired luminance.
In production of such an organic EL display device, a luminescent layer of a predetermined pattern made of an organic light-emitting material which emits light of the colors is formed for each organic EL element serving as a light-emitting element.
The organic EL layer and the second electrode can be prepared by, for example, (i) a vacuum vapor deposition method which uses a vapor deposition mask referred to as a shadow mask, (ii) an inkjet method, and (iii) a laser transfer method.
Among the methods listed above, the vacuum vapor deposition method is most typically used. According to the vacuum vapor deposition method, a vapor deposition material contained in a heating container called a crucible or a boat, is heated in a highly vacuum so as to be sublimated, and then a thin film made of the vapor deposition material is deposited on a substrate.
In this case, it is possible to form a vapor-deposited film only in a desired region of the substrate by (i) fixing a shadow mask in close contact with the substrate, the shadow mask being open in the desired region and (ii) vapor-depositing the vapor deposition material on the substrate via an opening of the shadow mask.
However, the vacuum vapor deposition method causes a loss of all the vapor deposition material except the vapor deposition material of which the vapor-deposited film deposited on the substrate is made. Therefore, the vapor deposition material except the vapor deposition material of which the vapor-deposited film deposited on the substrate is made is not made into a vapor-deposited film to be provided in an organic EL display device.
In other words, the vapor deposition material is all wasted which adheres to, for example, (i) a shutter which determines whether or not vapor deposition particles are emitted toward the substrate which is provided directly above, for example, the crucible containing the vapor deposition material, (ii) a vapor deposition preventing plate which is provided in a replaceable state so that an inside of a chamber of a vapor deposition device is not contaminated with the vapor deposition material, and (iii) a non-opening of the shadow mask.
The second electrode is typically made of metal, which is lower in unit material cost as compared to an organic material of which the organic EL layer is made. Meanwhile, the organic material of which the organic EL layer is made is a special functional material that possesses properties such as electroconductivity, a carrier transferring property, a light-emitting property, and thermal and electrical stability, and the organic material is extremely high in unit material cost.
Despite the above fact, all the vapor deposition material except the vapor deposition material of which the vapor-deposited film deposited on the substrate is made is lost (described earlier). This causes an increase in the amount of use of a material per substrate to be subjected to a vapor deposition process, so that a cost for the vapor deposition process is high, and consequently the organic EL display device increases in cost.
A method for solving such a problem may be exemplified by a method for collecting and reusing materials adherent to a part other than a substrate.
For example, Patent Literature 1 discloses a water jet device which causes water jet spraying to collect an adherent film adherent to a film formation jig.
FIG. 15 is a view schematically illustrating a configuration of the water jet device disclosed in Patent Literature 1.
The water jet device illustrated in FIG. 15 includes a table 126 which is a working table for carrying out a cleaning operation and a working chamber 122 which is box-shaped so as to cover the table 126 from above. The working chamber 122 has, on its side surfaces, doors via which a film formation jig 125 that is an object to be cleaned is carried in/out onto/from the table 126.
The working chamber 122 can be hermetically sealed so that during the cleaning operation, splashes of water jet can be prevented from leaking out of the working chamber 122.
The working chamber 122 includes a robot 121 which has a tip capable of three-dimensionally moving in accordance with a shape of a surface of the film formation jig 125 on which surface an adherent film is formed, the film formation jig 125 being an object to be cleaned (a cleaning target).
The robot 121 has an arm whose tip is provided with a cleaning gun 151. A high-pressure water generating device 152 for generating high-pressure water is provided outside and in proximity to the working chamber 122 so as to supply high-pressure water to the cleaning gun 151 via the robot 121.
Note that a pure water producing device 151 supplies, to the high-pressure water generating device 152, city water from which ions have been removed.
The working chamber 122 further includes a sprayer 159 for moistening an inner wall of the working chamber 122 and (ii) an exhaust fan 162 for setting a pressure inside the working chamber 122 to be negative.
The table 126 has many holes provided in a net-like pattern, and a centrifugal separator 157 is provided under the table 126. The centrifugal separator 157 includes a fixed container 154 and a rotating container 156. The rotating container 156 coaxially rotates at a high speed in the fixed container 154 whose skin has many holes and whose inner surface has a filtering member 155 which is provided so as to cover the many holes.
In a case where the cleaning gun 151 sprays water jet at a water pressure of 30 MPa to 200 MPa over the adherent film of the film formation jig 125 which is placed on a cleaning jig platen 153 provided on the table 126 of the working chamber 122, high-pressure water sprayed over the film formation jig 125 becomes suspended water containing adherent film pieces from the adherent film of the film formation jig 125.
Then, the suspended water, together with water burst from the sprayer 159, flows, directly or along an inner wall surface of the working chamber 122, downward via the many holes of the table 126, and then enters the rotating container 156, where the suspended water and the water burst from the sprayer 159 are subjected to centrifugation by the centrifugal separator 157, so as to be separated into adherent film pieces and wastewater. The adherent film can thus be collected.
Note that the wastewater from a drain 158 returns to the high-pressure water generating device 152 via a pipe 177.
Patent Literature 1 discloses that according to the water jet device, it is possible to collect and reuse the attached film of the film formation jig 125 while the film formation jig 125 is ground in a small amount and waste is generated in a reduced amount.